CASTING-ROLLING INTEGRATED PLANT AND METHOD FOR PRODUCING A HOT STRIP WITH A FINAL THICKNESS < 1.2 MM ON THE CASTING-ROLLING INTEGRATED PLANT

Abstract

A combined casting and rolling installation that produces hot-rolled strip with a final thickness<1.2 mm, and includes a first continuous casting installation and a second continuous casting installation, each producing slabs from liquid steel; a slab manipulator that conveys the slabs into a walking beam furnace that conveys the slabs into a rolling installation and heats the slabs to rolling temperature. The rolling installation includes a rough rolling mill forming rough-rolled strips from the heated slabs; a coil box forming a coil from the rough-rolled strip and unwinding the rough-rolled strip; a joining device forming an endless rough-rolled strip by connecting its ends without filler material; a multi-stand finishing rolling mill finish-rolling the endless rough-rolled strip to form a finished strip with the final thickness; a cooling section forming the hot-rolled strip; and a plurality of coiling devices coiling the hot-rolled strip.

Claims

1. A combined casting and rolling installation for producing hot-rolled strip with a final thickness<1.2 mm, preferably?1.0 mm, comprising: at least a first continuous casting installation and a second continuous casting installation, wherein each continuous casting installation casts liquid steel into slabs; a slab manipulator for conveying the slabs from the continuous casting installations into a walking beam furnace, the walking beam furnace conveying the slabs from the slab manipulator into a rolling installation and heating the slabs to rolling temperature, wherein slabs from the first continuous casting installation and slabs from the second continuous casting installation pass completely through the walking beam furnace and are uniformly heated in the process; the rolling installation, comprising, a rough rolling mill for rough rolling the heated slabs to form a rough-rolled strip, a preferably thermally insulated coil box for winding up the rough-rolled strip to form a coil and for unwinding the rough-rolled strip, a joining device for connecting, without filler material, a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip, a multi-stand finishing rolling mill for finish rolling the endless rough-rolled strip to form a finished strip with the final thickness, a cooling section for cooling the finished strip to form the hot-rolled strip, and a plurality of coiling devices for coiling the hot-rolled strip, wherein the roughing rolling mill, the coil box, the joining device, the multi-stand finishing rolling mill the cooling section and the coiling devices of the rolling installation are arranged in-line one behind the other, and the first continuous casting installation has a first offset in a first direction with respect to the rolling installation and the second continuous casting installation has a second offset in the first direction with respect to the rolling installation.

2. The combined casting and rolling installation as claimed in claim 1, wherein the continuous casting installations are configured to generate slabs with a thickness of 140 to 240 mm and a width of between 1100 and 2300 mm.

3. The combined casting and rolling installation as claimed in claim 1, wherein the roughing rolling mill is a reversing, preferably one-stand, roughing rolling mill.

4. The combined casting and rolling installation as claimed in claim 1, wherein the first direction is the horizontal.

5. The combined casting and rolling installation as claimed in claim 1, wherein the finishing rolling mill comprises five to seven finishing roll stands.

6. The combined casting and rolling installation as claimed in claim 1, wherein a first descaling device is arranged downstream of the walking beam furnace and upstream of the roughing rolling mill, and/or in that a second descaling device is arranged upstream of the joining device and a third descaling device is arranged upstream of the finishing rolling mill.

7. The combined casting and rolling installation as claimed in claim 1, wherein the slab manipulator can discharge slabs generated by the continuous casting installations transversely with respect to the conveying direction from the continuous casting installations to the walking beam furnace, and the slab manipulator can introduce slabs which have not been generated in the continuous casting installations of the combined casting and rolling installation transversely with respect to the conveying direction from the continuous casting installations to the walking beam furnace.

8. A method for producing a hot-rolled strip with a final thickness<1.2 mm, preferably ?1.0 mm, on a combined casting and rolling installation, in particular as claimed in one of the preceding claims, comprising the following steps: continuously casting liquid steel into slabs on at least a first continuous casting installation (1a) and a second continuous casting installation; conveying the slabs from the continuous casting installations into an inlet region of a walking beam furnace; conveying the slabs from the inlet region through the walking beam furnace into an outlet region of the walking beam furnace, wherein the slabs are heated to rolling temperature; rough rolling the heated slabs to form a rough-rolled strip; winding up the rough-rolled strip to form a coil and preferably thermally insulating, particularly preferably heating, the coil; unwinding the rough-rolled strip from the coil; connecting, without filler material, a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip; finish rolling the endless rough-rolled strip to form a finished strip with the final thickness by way of multiple rolling passes in a multi-stand finishing rolling mill; cooling the finished strip to form the hot-rolled strip; cutting the hot-rolled strip; and coiling the hot-rolled strip.

9. The method as claimed in claim 8, wherein the rough rolling is effected by way of multiple, preferably 3-5, rolling passes in a reversing roughing rolling mill.

10. The method as claimed in claim 8, wherein when connecting the rough-rolled strips to form the endless rough-rolled strip, the foot of the leading rough-rolled strip is firstly overlapped with a head of the trailing rough-rolled strip, and then the overlapping region of the rough-rolled strips is compressed, wherein the vertical positions of the rough-rolled strips are aligned with one another.

11. The method as claimed in claim 8, wherein the rough-rolled strips are descaled after the unwinding and prior to the connecting.

12. The method as claimed in claim 8, wherein the slabs have a thickness of 140 to 240 mm and a width of between 1100 and 2300 mm, and/or the rough-rolled strip has a thickness of between 25 and 35 mm.

13. The method as claimed in claim 8, wherein the slabs are charged at a temperature?900? C. into the walking beam furnace.

14. The method as claimed in claim 8, wherein the combined casting and rolling installation has an annual production capacity of between 3 and 6 million tons, in particular between 3.5 and 5.5 million tons.

15. The method as claimed in claim 8, wherein the continuous casting installations produce slabs with a thickness of 150 to 190 mm at a casting rate of 4 to 5 m/min and slabs with a thickness of 191 to 230 mm at a casting rate of 2 to 4 m/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The above-described properties, features and advantages of this invention, and the manner in which these are achieved, will become clearer and more clearly understandable in conjunction with the following description of an exemplary embodiment, which will be explained in more detail in conjunction with the drawings, in which:

[0066] FIG. 1 shows a schematic diagram of a combined casting and rolling installation,

[0067] FIG. 1a shows a front portion of the combined casting and rolling installation from FIG. 1,

[0068] FIG. 1b shows a central portion of the combined casting and rolling installation from FIG. 1,

[0069] FIG. 2 shows an elevation illustration of the combined casting and rolling installation from FIG. 1, and

[0070] FIG. 3 shows a schematic illustration of the steps when joining two rough-rolled strips to form an endless rough-rolled strip.

DESCRIPTION OF THE EMBODIMENTS

[0071] The combined casting and rolling installation according to the invention is schematically illustrated in FIGS. 1, 1a and 1b. The combined casting and rolling installation comprises two continuous casting installations 1a and 1b (it is of course also possible to have more than two continuous casting installations) which are connected to a rolling installation 5 by way of a slab manipulator 3 and a walking beam furnace 4. On each continuous casting installation 1a, 1b, liquid steel is cast into slabs 2. The continuous casting installations each comprise a mold, an arcuate strand guide and a horizontal run-out region which is enclosed in a thermal insulation 13. The slab strands of the continuous casting installations 1a and 1b are cut by shears into slabs with a length of between 11.5 and 26 m, normally approximately 14 m. The produced slabs 2 are conveyed by the slab manipulator 3 in the horizontal direction into the gas-fired walking beam furnace 4, heated to rolling temperature there and conveyed to the rolling installation 5.

[0072] In the inlet region of the rolling installation 5, the slab 2 is firstly descaled by a first descaling device 12a and then rolled by a one-stand, reversing roughing rolling mill 6 by way of 3 to 5 rolling passes to form a rough-rolled strip. Subsequently, the rough-rolled strip is wound up in the preferably thermally insulated coil box 7 to form a coil. After the coil box has been pivoted by 180?, the coil is unwound again and fed to the joining device 8. In order to ensure reliable connection of the rough-rolled strips, the rough-rolled strips are partially descaled by a second descaling device 12b. In the joining device 8, a foot of a leading rough-rolled strip is connected to the head of a trailing rough-rolled strip to form an endless rough-rolled strip (see also FIG. 3).

[0073] The endless rough-rolled strip is then descaled by a third descaling device 12c and finish rolled in the five-stand finishing rolling mill to form a finished strip with the final thickness of 0.8 mm. The finished strip is then cooled in the cooling section 10, cut by high speed shears (or flying shears) and wound up by a plurality ofhere for example threecoiling devices 11a . . . 11c.

[0074] Between the first descaling device 12a and the roughing rolling mill 6, the roughing rolling mill 6 and the coil box 7 and in the region of the coil box 7, the slabs 2, the rough-rolled strip and the coiled rough-rolled strip, respectively, are thermally insulated. Depending on the grade of steel produced, it may also be necessary to not cool the hot-rolled strip in the cooling section 10 but to thermally insulate it.

[0075] According to the invention, a plurality of continuous casting installations (here 1a, 1b) produce the required mass flow of 3.5 to 5.5 M t/a. The discrete slabs are heated to rolling temperature by way of the slab manipulator and the walking beam furnace and fed to the rolling installation 5. In the rolling installation 5, firstly a coil of a rough-rolled strip is produced from a slab 2 by rough rolling. The coil is then unwound again and the head of the trailing, i.e. unwound, rough-rolled strip is connected to the foot of a leading rough-rolled strip to form an endless rough-rolled strip. The connecting is effected by joining, specifically by compressing the rough-rolled strips, without these being welded to one another by way of a filler material. The endless rough-rolled strip is finish rolled in endless operation in the finishing rolling train, as a result of which it is possible to generate ultrathin hot-rolled strips with a thickness<1.2 mm, preferably even ?1.0 mm, without any problems.

[0076] FIG. 2 shows an elevation illustration of the combined casting and rolling installation from FIG. 1. It can be seen that the horizontal run-out regions of the two continuous casting installations 1a and 1b lie at approximately the same height in the vertical direction as the inlet region of the rolling installation 5. However, no continuous casting installation is connected in-line with the rolling installation 5, since the slabs 2 are firstly brought via the slab manipulator 3 and then the walking beam furnace 4 into the rolling installation. This ensures that the slabs have a constant temperature, regardless of whether they have been produced in the first or the second continuous casting installation 1a, 1b or even have been introduced externally into the slab manipulator. Specifically, the run-out region of the first continuous casting installation 1a has a greater offset A1 in the horizontal direction with respect to the rolling installation 5 than the offset A2 in the horizontal direction between the run-out region of the second continuous casting installation 1b and the rolling installation 5.

[0077] FIG. 3 illustrates the steps when joining two rough-rolled strips 20, 21 to form an endless rough-rolled strip. Firstly, the head of the trailing rough-rolled strip 21 is superimposed with the foot of the leading rough-rolled strip 20, such that an overlapping region 23 is produced. Subsequently, the rough-rolled strips 20, 21 are pressed against one another by pressing and supporting forces 24, 25, wherein cutting edges 22 act on the lower side of the leading rough-rolled strip 20 and on the upper side of the trailing rough-rolled strip 21. The pressing together and cutting of the rough-rolled strips 20, 21 produces an endless rough-rolled strip in the central region and two portions 26 above and below the central region. The portions are removed either mechanically or by fluid jets of the second descaling device 12b and finish rolled.

[0078] Although the invention has been illustrated and described in more detail by the preferred exemplary embodiments, the invention is not limited by the examples disclosed, and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

LIST OF REFERENCE DESIGNATIONS

[0079] 1 Continuous casting installation [0080] 1a First continuous casting installation [0081] 1b Second continuous casting installation [0082] 2 Slab [0083] 3 Slab manipulator [0084] 4 Walking beam furnace [0085] 5 Rolling installation [0086] 6 Roughing rolling mill [0087] 7 Coil box [0088] 8 Joining device [0089] 9 Finishing rolling mill [0090] 10 Cooling section [0091] 11a . . . 11c Coiling device [0092] 12a First descaling device [0093] 12b Second descaling device [0094] 12c Third descaling device [0095] 13 Thermal insulation [0096] 20 Leading rough-rolled strip [0097] 21 Trailing rough-rolled strip [0098] 22 Cutting edge [0099] 23 Overlapping region of the rough-rolled strips [0100] 24 Pressing force [0101] 25 Supporting force [0102] 26 Portions [0103] A1, A2 First offset, second offset